Date of Award

1993

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Plant Pathology and Crop Physiology

First Advisor

Edward C. McGawley

Abstract

The interrelationships between the reniform nematode, Rotylenchulus reniformis Linford and Oliveira, and the fungus Rhizoctonia solani Kuhn were studied on cotton (Gossypium hirsutum L.). Parasitism of cotton seedlings by R. solani resulted in enhanced reproduction of R. reniformis. In the presence of the fungus, there was increased egg production by the nematode which resulted in augmented soil population density. Enhanced reproduction of the nematode in the presence of the fungus was consistent across isolates of R. solani, populations and inoculum levels of R. reniformis, and cotton cultivars. The nematode did not influence the severity of seedling blight disease. At 90 days, when R. solani and R. reniformis were present together, effects on cotton growth were antagonistic. Culture filtrates of R. solani obtained from potato dextrose broth were inhibitory to the hatching of eggs of R. reniformis, and the medium was more inhibitory than the filtrate. Filtrates of R. solani collected from sterile deionized distilled water did not affect egg hatching. Root exudates from cotton seedlings increased the hatching of eggs of R. reniformis. Exudates from the root systems of R. solani infected and noninfected cotton seedlings did not differ in their effect on egg hatching. However, infectivity of preadult females to cotton seedlings was significantly augmented in the presence of Rhizoctonia solani.

Pages

70

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